Firestore array-contains doesn't work with cloud firebase admin

Question

I have the below data structure for the members property in my teams collection.

and I am trying to write the below query via triggers to update the structure whenever there is an update on the members collection.

const teamData = await firebaseAdmin
        .firestore()
        .collection('teams')
        .where('members', 'array-contains', { id: change.after.id })
        .get();

But this always returns an empty set of collections even though the data matches. I referred this post and then tried as below wherein I had compared complete object with the data available in the before context. But again even that would return the empty result set.

const memberBefore = change.before.data() as Member;
const teamData = await firebaseAdmin
        .firestore()
        .collection('teams')
        .where('members', 'array-contains', [
          {
            id: change.after.id,
            name: memberBefore.name,
            nameKa: memberBefore.nameKa,
            img: memberBefore.img,
          },
        ])
        .get();

Could someone help me out to resolve this issue?

Answer 1

arrayContains does NOT match subfields - it matches the entire entry. And to be totally honest, Firestore "arrays" are ABSOLUTELY NOT ARRAYS - they are "ordered lists" - the "number" is their order, not an index. I suspect, also, that the ORDER of the entries in the object are important, as well, so your screenshot order:

{
id: "xxxxxx",
img: "xxxxx",
name: "xxxxx",
nameKa: "xxxxx"
}

WILL NOT MATCH

{
id: change.after.id,
name: memberBefore.name,
nameKa: memberBefore.nameKa,
img: memberBefore.img,
}

Firestore's scale and speed come from indexing entries, and an "array" (ordered list) of objects is essentially indexed by a string-like representation of the object.

Firestore "arrays" (ordered lists) of objects are remarkably difficult to use, and give you no advantages - they are much better suited to "single value" entries. I would strongly recommend using a sub-collection of documents (each member in it's own document), where you can trivially query (either a a collection or collectionGroup) to find individual documents.